In an apparatus that handles banknotes, such as a banknote recognition unit provided in a cash handling machine or the like and an automatic vending machine, it is important to recognize a banknote altered by a tape, paper or the like, and the banknote recognition unit is provided for the recognition.
The banknote altering techniques have been sophisticated particularly in recent years. For example, banknotes, securities, stamps, and checks altering by a tape, paper, or seal have been circulated.
As an example of a banknote judgment unit that authenticates banknotes or the like altered by a tape, paper or the like, there is a conventional technique described in Japanese Utility Model Application Laid-open No. H6-49442, for example.
A paper-sheet-thickness detecting device in this conventional technique is explained with reference to FIG. 11. As shown in FIG. 11, a reference roller 101 and a detection roller 102 are provided to face each other, and the detection roller 102 is attached to one end of a lever member 104 swingable vertically around a fulcrum shaft 103 by a movable shaft 105, and a douser 106 is attached to the other end of the lever member 104. An optical sensor 107 such as a photo interrupter is arranged facing to the douser 106. The lever member 104 is biased upward by a spring 108 at a position away from the movable shaft 105, putting the fulcrum shaft 103 therebetween, and the detection roller 102 is pushed down by this bias. However, the lever member 104 is locked by a locking member 109 so that a gap d between the detection roller 102 and the reference roller 101 becomes wider than a thickness t of a paper sheet P and narrower than a thickness 2t of two paper sheets.
Therefore, if only one paper sheet P is inserted, the movable shaft 105 does not move vertically, and there is no change in a detection result of the optical sensor 107. If two paper sheets are inserted together, the detection roller 102 is pushed upward to move the douser 106 via the lever member 104, and the detection result of the optical sensor 107 changes. The thickness of the paper sheet is detected with this configuration.
In the conventional technique, however, a setting operation of the gap d between the detection roller 102 and the reference roller 101 becomes quite difficult. Further, even if the gap d can be accurately set, the gap d may often go out of order during use.
Furthermore, in the conventional technique, the detection roller is always brought into contact with the reference roller. However, if the detection roller is always brought into contact with the reference roller, a tremor (pitching) of the detection roller occurs during passage of a paper sheet, thereby causing a problem such that the thickness cannot be detected accurately.
Further, when the paper sheet passes through between the detection roller and the reference roller, fine dust adhered to the surface of the paper sheet adheres to the detection roller and the reference roller, and if the roller is coated with the dust, accurate detection cannot be performed. Regarding this problem, a scraper for removing a foreign substance is disclosed in Japanese Laid-open Patent Publication No. H10-283520. However, if the scraper is secured to a part of an apparatus, even in the case of an elastic scraper, a movement of a detection roller when a banknote comes in between the rollers is blocked due to an end of the scraper, and thus accurate thickness detection cannot be performed.
Moreover, when thickness detection is performed for the entire surface of a paper sheet by arranging a plurality of detection blocks including the detection rollers in a direction orthogonal to a transport direction of the paper sheet so that the detection rollers come into contact with the entire surface of the transported paper sheet, the paper sheet bumps against all the detection rollers at a time. Therefore, the detection blocks move abruptly due to a shock thereof, and a kick appears in an acquired detection output waveform. Furthermore, there is such a problem that paper jam occurs due to a resistance when the paper sheet bumps against the detection roller.